JP6852609B2 - Glass substrate, organic EL lighting device - Google Patents

Description

The present invention relates to a glass substrate and an organic EL lighting device including a glass substrate.

The organic EL (Electro Luminescence) element is a self-luminous element capable of surface emission, and is used in a thin illumination light source, a flat panel display, and the like. This organic EL element has a thin film laminated structure in which a transparent conductive layer such as ITO, an organic layer including a light emitting layer, a metal conductive layer and the like are formed on a transparent substrate such as a glass substrate, and the transparent conductive layer and the metal conductive layer are provided. The layers are used as a pair of electrodes (electrode and cathode), and the light emitted by energization between the electrodes is taken out to the outside through a transparent substrate.

In such an organic EL element, since the refractive index of the organic layer or the transparent conductive layer is considerably higher than the refractive index of the transparent substrate, a part of the light emitted by the organic layer is at the interface between the transparent conductive layer and the transparent substrate or. A phenomenon occurs in which total reflection occurs at the interface between the transparent substrate and the air layer and is confined inside the element, and all the emitted light cannot be taken out to the outside. The ratio of light that can be extracted to the outside with respect to the emitted light is called the light extraction efficiency. Organic EL devices that want to improve the light extraction efficiency to obtain the highest possible brightness with low power consumption, especially organic EL. It has become a major issue for lighting equipment.

As a measure to improve the light extraction efficiency, it is necessary to consider two aspects: increasing the amount of light entering the inside of the transparent substrate and increasing the amount of light entering the transparent substrate that is emitted from the surface of the transparent substrate. Become. As a remedy for the former, it is considered to provide a refractive index adjusting layer having a light scattering function between the transparent conductive film and the transparent substrate. For example, a transparent substrate is formed by blending a refractive index adjusting particle and a binder. It has been proposed to disperse scattered particles formed of a transparent material having a refractive index different from that of the base material portion in the base material portion adjusted to a higher refractive index (the following patent documents). 1).

Further, as a remedy for the latter, it is considered to provide an uneven shape on the surface of the transparent substrate on the light extraction side. For example, the surface of the transparent substrate is convex or concave and has an apex angle of 20. It has been proposed to provide a cone-shaped lens array element set in the range of ° to 120 ° (see Patent Document 2 below).

Japanese Unexamined Patent Publication No. 2015-176734 Japanese Unexamined Patent Publication No. 2003-59641

In order to improve the light extraction efficiency of the organic EL element, it is conceivable to combine the former improvement measures and the latter improvement measures described above. However, when a refractive index adjusting layer having a light diffusion function is provided on the back surface side (light incident side) of the transparent substrate, the traveling direction of the light incident on the transparent substrate is wide in various directions due to the effect of light scattering. Will have a distribution. On the other hand, on the surface side (light extraction side) of the transparent substrate, a concavo-convex shape (lens array element) having a constant apex angle (constant angle set in the range of 20 ° to 120 °) is provided. Therefore, there is a problem that the light traveling in various directions inside the transparent substrate cannot be efficiently taken out.

An object of the present invention is to solve such a problem. That is, in the glass substrate which is the transparent substrate on the light extraction side of the organic EL element, more light is taken into the inside of the glass substrate, and the light incident on the glass substrate is efficiently extracted to the outside to extract the light of the organic EL element. It is an object of the present invention to improve efficiency.

In order to solve such a problem, the present invention has the following configurations.
A glass substrate that is a transparent substrate on the light extraction side of an organic EL element. A refractive index adjusting layer having a light scattering function is provided on the light incident side of the glass layer, and a flat surface is provided on the light emitting side of the glass layer. A glass substrate characterized in that a surface shaping having an angle distribution with respect to a glass substrate is provided.

The glass substrate having such characteristics has a refractive index adjusting layer having a light scattering function, and on the surface of the glass layer on the light incident side, the light once reflected there changes the angle again and enters the glass layer. As a result, a large amount of light can be taken into the glass layer. At this time, the traveling direction of the light incident on the glass layer has a wide distribution in various directions, but by providing a surface shaping having an angular distribution with respect to the flat surface on the light emitting side of the glass layer. , Light traveling in various directions in the glass layer can be efficiently taken out to the outside. This makes it possible to provide a glass substrate capable of improving the light extraction efficiency of the organic EL element.

An explanatory view showing a glass substrate according to an embodiment of the present invention ((a) is a cross-sectional view, (b) is an enlarged view of part A of (a)). It is explanatory drawing which showed the structural example of the organic EL element (organic EL lighting apparatus). It is explanatory drawing of an Example ((a) is a histogram which showed the angular distribution of a shaping A, (b) is a histogram which showed the angular distribution of a shaping B). 3 is a graph showing the cumulative power of the histograms of FIGS. 3A and 3B for each angle.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the glass substrate includes a glass layer 1 and a refractive index adjusting layer 2. The glass layer 1 is provided with a surface shaping 1A on the light emitting side (front surface side) and a rough surface 1B on the light incident side (back surface side). The refractive index adjusting layer 2 is provided on the light incident side of the glass layer 1.

The refractive index adjusting layer 2 has a resin layer 2A having a higher refractive index than the glass layer 1 and scattered particles 2B having a refractive index different from the refractive index of the resin layer 2A, and has a function of scattering transmitted light ( It has a light scattering function). The scattered particles 2B have a particle size similar to that of visible light. Specifically, those having a particle size of 0.1 to 2.5 μm can be used, and the particle size may be uniform or non-uniform. Further, the scattered particles 2B are mixed in the resin layer 2A in the range of a volume fraction of 20 to 80%, and can be composed of silicone particles as an example. However, the material of the scattered particles 2B is not limited to silicone particles as long as the material has a different refractive index from that of the refractive index adjusting layer 2. For example, ceramics such as glass can be used.

The refractive index adjusting layer 2 is formed on the rough surface 1B on the back surface side of the glass layer 1 and serves as a base layer of the transparent conductive layer which is a component of the organic EL element, and is equal to or lower than the refractive index of the transparent conductive layer. Has a refractive index higher than that of the glass layer 1. Further, the refractive index adjusting layer 2 has a function of filling and flattening the rough surface 1B of the glass layer 1 so that the transparent conductive layer formed on the transparent conductive layer 2 becomes flat. Further, the material used for the refractive index adjusting layer 2 is not limited to resin as long as it is a transparent material. For example, ceramics such as glass can be used.

The surface shaping 1A formed on the surface of the glass layer 1 has various angular distributions with respect to the flat surface H of the glass substrate. In this surface shaping 1A, a plurality of concave or convex unit shapes are arranged in parallel, and various angular distributions are provided at the interface with the air layer in one unit shape.

FIG. 2 shows a configuration example of the organic EL element including the glass substrate described above. In the organic EL element, the transparent conductive layer 3 is formed on the refractive index adjusting layer 2 provided on the back surface side of the glass layer 1, the organic layer 4 having a light emitting layer is formed on the transparent conductive layer 3, and the organic layer 4 is formed. A metal conductive layer 5 is formed on the metal conductive layer 5. Such an organic EL element becomes a light emitting element of an organic EL lighting device.

The organic EL element has a transparent conductive layer 3 and a metal conductive layer 5 as a pair of electrodes, and the light emitted from the light emitting layer by energizing between the electrodes is the transparent conductive layer 3, the refractive index adjusting layer 2, and the glass layer 1. It passes through and is taken out to the outside. At this time, due to the refractive index adjusting layer 2 having a light scattering function, on the surface of the glass layer 1 on the light incident side, the light once reflected there tries to change the angle again and enter the glass layer 1, resulting in a result. A lot of light is taken into the glass layer 1. Here, the traveling directions of the light incident on the glass layer 1 have a wide distribution in various directions, but the surface shaping 1A having an angular distribution with respect to the flat surface is provided on the light emitting side of the glass layer 1. By providing the light, the light traveling in various directions in the glass layer 1 can be efficiently taken out to the outside. This makes it possible to improve the light extraction efficiency of the organic EL element.

An embodiment will be described below. The surface shaping 1A formed on the glass layer 1 is formed by pressing a convex shape of a quadrangular pyramid (pyramid shape) against the glass layer 1 in a molten state. At this time, a shape A having a shape depth of about 20 μm and a shape B having a shape depth of about 50 μm are formed.

When the surface shaping 1A formed on the glass layer 1 forms the above-mentioned shaping A, an angular distribution as shown in the histogram of FIG. 3A is formed within one unit shape. .. Here, the angle 0 ° is an angle parallel to the flat surface of the glass substrate, and the angle 90 ° is an angle orthogonal to the flat surface of the glass substrate, and the class width of the histogram is 1 °. The angular distribution of the shape A has the highest frequency of 1 °, and is mainly distributed in the range of 0 ° to 30 °, but the peak frequency of the histogram is 16% or less.

On the other hand, the surface shaping 1A formed on the glass layer 1 has an angle as shown in the histogram of FIG. 3B within one unit shape when the above-mentioned shaping B is formed. A distribution is formed. The angle distribution of the shape B is most frequently at an angle of 4 ° to 8 ° (about 5 to 6% each) when the class width of the histogram is 1 °, and is in the range of an angle of 0 ° to an angle of 70 °. Although it is widely distributed, the peak frequency of the histogram is 6% or less.

FIG. 4 is a graph showing the cumulative power of the histograms of FIGS. 3A and 3B for each angle. It can be seen that the shape B shows a distribution in a wide angle range with respect to the shape A. As for the cumulative frequency, in the angular distribution of the shape A, the angle of 50% or more is 3 °, and in the angle distribution of the shape B, the angle of 50% or more is 9 °.

Then, the shaping A is adopted as the surface shaping 1A of the glass layer 1, and the scattering particles (silicone particles) 2B having a particle size of 0.2 to 2 μm are used as the refractive index adjusting layer 2 as the resin layer 2A with a volume fraction of 44%. The glass substrate dispersed in the above is designated as Example 1. Further, the shaping B is adopted as the surface shaping 1A of the glass layer 1, and the scattered particles (silicone particles) 2B having a particle size of 0.2 to 2 μm are similarly used as the refractive index adjusting layer 2 at a volume fraction of 44%. The glass substrate dispersed in the resin layer 2A is referred to as Example 2.

Then, an organic EL element is formed on the glass substrate of Example 1 and the glass substrate of Example 2, respectively, and the light extraction efficiency is measured, and the measured value is measured on the flat glass substrate (the material of the glass layer is the same). An organic EL element was formed and the light extraction efficiency was measured and compared with the measured value. In addition, the light extraction efficiency of an organic EL element in which a commercially available film for improving the light extraction efficiency is attached to the surface of a flat glass substrate is measured, and the measured value and the organic EL on the flat glass substrate (the material of the glass layer is the same). The element was formed and the light extraction efficiency was measured and compared with the measured value. The measurement results are shown in the table below.

As is clear from Table 1, both Examples 1 and 2 have higher light extraction efficiency than the flat glass substrate, and Example 1 has the same light extraction efficiency as when a commercially available film is attached. In Example 2, even higher light extraction efficiency is obtained as compared with the case where a commercially available film is attached.

Since the light extraction efficiency of the second embodiment is higher than that of the first embodiment, when the refractive index adjustment 2 having a light scattering function is provided on the back surface side of the glass layer 1, the surface shaping of the glass layer 1 is performed. It was found that high light extraction efficiency can be obtained by dispersing the angle distribution of 1A over a wider angle range, that is, by lowering the peak frequency of the angle distribution histogram. In Form A of Example 1, the peak frequency of the histogram at a class width of 1 ° is 16% or less of the total, but a commercially available film that improves the light extraction efficiency by dispersing the angle distribution to the same extent. It is possible to obtain the same level of light extraction efficiency as in the case of pasting, and by further lowering the ratio of the peak frequency as in the modified B, a higher light extraction efficiency can be obtained.

In the above-described embodiment, the shape of the surface shaping 1A is a shape in which a quadrangular pyramid is pushed in, but the shape of the surface shaping 1A is not limited to this, as long as the angle distribution is widely dispersed. It may have any shape.

1: Glass layer, 1A: Surface shaping, 1B: Rough surface,
2: Refractive index adjustment layer, 2A: Resin layer, 2B: Scattered particles,
3: Transparent conductive layer, 4: Organic layer (light emitting layer), 5: Metal conductive layer

Claims (5)

A glass substrate that is a transparent substrate on the light extraction side of an organic EL element.
On the light incident side of the glass layer has a refractive index adjustment layer having a light scattering function is provided on the light emission side of the glass layer, the surface shaping having an angular distribution is provided,
The angle of the angle distribution is defined as an angle of 0 ° when it is parallel to the flat surface of the glass substrate and an angle of 90 ° when it is orthogonal to the flat surface of the glass substrate.
The angle distribution within one unit shape of the surface shaping is a glass substrate characterized in that the frequencies of all the classes are dispersed to 16% or less in a histogram in which the class width is 1 °. The first aspect of claim 1, wherein the angle distribution within one unit shape of the surface shaping is configured such that the cumulative power of the class having an angle of 3 ° or more is 50% or more in the cumulative power of the histogram. Glass substrate. The glass substrate according to claim 1 or 2, wherein scattered particles having a particle size of 0.1 to 2.5 μm are dispersed in the refractive index adjusting layer in a volume fraction of 20 to 80%. The glass substrate according to any one of claims 1 to 3, wherein the surface of the glass layer on the light incident side is a rough surface. An organic EL lighting apparatus comprising the glass substrate according to any one of claims 1 to 4, wherein a transparent conductive film is formed on the refractive index adjusting layer.

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